Base Station Device, Mobile Communication Method, and Mobile Communication System

1. A base station device for making communications with a mobile terminal, the base station device comprising: a communication monitoring unit that monitors a communication situation between the base station device and the mobile terminal; and an operational-power control unit that causes, when the communication monitoring unit detects that no communication between the base station device and the mobile terminal being present in a communication area which the base station device forms have been made for a predetermined continuous period or longer while the base station device is in a first mode where the base station device transmits broadcast information at a first power, the base station device to shift to a second mode where the base station device transmits the broadcast information at a second power lower than the first power, the communication area being formed both indoors and outdoors in the first mode, and the communication area being formed only indoors in the second mode.

2. The base station device according to claim 1 , wherein, when a connection request is received from the mobile terminal while the base station device is in the second mode, the operational-power control unit causes the base station device to shift to the first mode.

3. The base station device according to claim 1 , wherein, the operational-power control unit causes the base station device to shift to the first mode when a connection request is received from the mobile terminal that is permitted to access the base station device while the base station device is in the second mode, and causes the base station device to continue the second mode when the connection request is received from the mobile terminal that is not permitted to access the base station device while the base station device is in the second mode.

4. The base station device according to claim 1 , wherein, when a connection request is received from a higher-level device to connect the base station device to the mobile terminal while the base station device is in the second mode, the operational-power control unit causes the base station device to shift to the first mode.

5. The base station device according to claim 1 , wherein, the operational-power control unit causes the base station device to shift to the first mode when a connection request is received from a higher-level device to connect the base station device to the mobile terminal that is permitted to access the base station device while the base station device is in the second mode, and causes the base station device to continue the second mode when the connection request is received from the higher-level device to connect the base station device to the mobile terminal that is not permitted to access the base station device while the base station device is in the second mode.

6. A mobile communication method performed by a base station device that communicates with a mobile terminal, the mobile communication method comprising: monitoring a communication situation between the base station device and the mobile terminal; and causing, when it is detected at the monitoring that no communication between the base station device and the mobile terminal being present in a communication area which the base station device forms have been made for a predetermined continuous period or longer while the base station device is in a first mode where the base station device transmits broadcast information at a first power, the base station device to shift to a second mode where the base station device transmits the broadcast information at a second power lower than the first power, the communication area being formed both indoors and outdoors in the first mode, and the communication area being formed only indoors in the second mode.

7. A mobile communication system comprising: a base station device; and a mobile terminal that makes communications with the base station device, wherein the base station device includes: a communication monitoring unit that monitors a communication situation between the base station device and the mobile terminal; and an operational-power control unit that causes, when the communication monitoring unit detects that no communication between the base station device and the mobile terminal being present in a communication area which the base station device forms have been made for a predetermined continuous period or longer while the base station device is in a first mode where the base station device transmits broadcast information at a first power, the base station device to shift to a second mode where the base station device transmits the broadcast information at a second power lower than the first power, the communication area being formed both indoors and outdoors in the first mode, and the communication area being formed only indoors in the second mode.